The present invention relates to customising surgical apparatus and in particular to customising surgical instruments and/or implants using patient specific data obtained from a captured image of a patient.
The general idea of creating a patient specific instruments or implants from CT or MRI data has been described previously, for example in U.S. Pat. No. 5,768,134 and WO 93/25157. U.S. Pat. No. 5,768,134 describes using a CT scanner or MRI scanner to generate digitized medical information, which can be used with additional digital information, and a rapid prototyping method to create a prosthesis matching a body part and to which a further functional element can be attached. WO 93/25157 describes a method using tomographic data, such as from a CT or MRI scan, and image processing to generate a 3D reconstruction of the body part, which can be used with a CNC machine to allow an individual prostheses to be created. An individual template can also be manufactured matching a patient's anatomy and for mounting on the patient for guidance, alignment and positioning of a treatment tool.
However, not all medical facilities have access to CT or MRI scanners. In many cases, CT or MRI data of a patient is not available. Further, CT scans entail a significant radiation dose for patients and so should be avoided where possible. Further in many countries, regulations require the scans to be diagnosed by a specialist radiologist. Furthermore, CT and MRI scans are data processing intensive and require a large amount of processing time in order to derive patient specific data from the scans. Processing of the data can not be fully automated due to the variability in data quality and the accuracy in surface reconstructions required thus making such an approach unsuitable for a large-scale production scheme.
Other approaches to generating a 3D model of a patient's anatomy exist. For example statistical shape model and other deformable model based approaches can be used for modelling patient's actual bone shapes. For example, U.S. Pat. No. 7,194,295 describes a method for computer assisted navigation and/or pre-operative treatment planning in which a generic model of the patient's body part is adapted based on patient characteristic data which can be obtained from X-ray images of the patient. US2005/0027492 describes a method of building a statistical shape model by establishing correspondences between sets of two dimensional or three dimensional shapes. However, the approaches described in these documents have not in themselves been able to generate 3D models which can efficiently be used to replace CT or MRI scans in the above described methods. Such modelling approaches do not in themselves produce the surface accuracy, for example 1-2 mm, generally required for customising implants or instruments.
Therefore, it would be desirable to be able to provide customised implants, instruments or surgical procedures without using a CT or MRI, or similar, 3D scanning approach.